How do I declare a multi-dimensional array in C++?

Question

The following is an example of a multi-dimensional array declaration in C#:

var Number = new double[2, 3, 5]
    {
        {
             {  12.44, 525.38,  -6.28,  2448.32, 632.04 },
             {-378.05,  48.14, 634.18,   762.48,  83.02 },
             {  64.92,  -7.44,  86.74,  -534.60, 386.73 }
        },
        {
             {  48.02, 120.44,   38.62,  526.82, 1704.62 },
             {  56.85, 105.48,  363.31,  172.62,  128.48 },
             {  906.68, 47.12, -166.07, 4444.26,  408.62 }
        },
    };

I would like to do the same in C++, but do not know how and have not read my C++ book.

How can I accomplish this?

Any effort to show us? At all? – Lightness Races in Orbit Jan 31 '13 at 00:23 — Lightness Races in Orbit, Jan 31 '13 at 00:23

Andy Prowl · Accepted Answer · 2013-01-31T00:14:19.453

1

Here is a naive way of doing that without explicitly specifying the bounds:

vector<vector<vector<double>>> v =
{
    {
        {  12.44, 525.38,  -6.28,  2448.32, 632.04 },
        {-378.05,  48.14, 634.18,   762.48,  83.02 },
        {  64.92,  -7.44,  86.74,  -534.60, 386.73 }
    },
    {
        {  48.02, 120.44,   38.62,  526.82, 1704.62 },
        {  56.85, 105.48,  363.31,  172.62,  128.48 },
        {  906.68, 47.12, -166.07, 4444.26,  408.62 }
    },
};

However, the vector of vectors will allow you to push elements into each dimension freely (they are just independent vectors), so you might end up not having a consistent multi-dimensional vector. In particular, the compiler won't detect any attempt to put more or less elements into one dimension than into another one.

If that is a concern, you might want to check Boost.MultiArray.

edited Jan 31 '13 at 00:14

answered Jan 31 '13 at 00:03

Andy Prowl

124,023
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not array i meant as std::vectro>> foo; – user522745 Jan 31 '13 at 00:04
@user522745: Sorry for the misunderstanding, I fixed my answer. Hope it helps. – Andy Prowl Jan 31 '13 at 00:13
Not to mention the potentially horrible performance hit you get from using vectors of vectors (of vectors...). – Ed S. Jan 31 '13 at 00:26
1

@user522745, whom are you calling foo buddy? – thang Jan 31 '13 at 00:28

score 0 · Answer 2 · answered Jan 31 '13 at 02:03

You don't need the standard library, or Boost, to define and initialize a fixed size multidimensional array.

double Number[2][3][5] =
    {   
        {   
             {  12.44, 525.38,  -6.28,  2448.32, 632.04 },
             {-378.05,  48.14, 634.18,   762.48,  83.02 },
             {  64.92,  -7.44,  86.74,  -534.60, 386.73 }
        },  
        {   
             {  48.02, 120.44,   38.62,  526.82, 1704.62 },
             {  56.85, 105.48,  363.31,  172.62,  128.48 },
             {  906.68, 47.12, -166.07, 4444.26,  408.62 }
        },  
    };

How do I declare a multi-dimensional array in C++?

2 Answers2